Context <p>Range shifts and altered dominance patterns of habitat-forming species are changing the seascape structure of temperate marine ecosystems. Yet, the role of intraspecific interactions in mediating establishment and growth of newly arriving populations at range-edges remains poorly understood, limiting predictions of persistence in marginal habitats.</p> Objectives <p>We examined the spatial demography of the coral <i>Pocillopora aliciae</i> at its poleward range limit in Sydney, Australia (34 S). Over five-years, we quantified the spatiotemporal dynamics of adults and juveniles to identify the demographic mechanisms underpinning coral establishment and local expansion on temperate rocky reefs.</p> Methods <p>Structure-from-motion photogrammetry was applied between 2019 and 2024 to quantify changes in density, size structure, and spatial configuration of corals. Corals were segmented from large-area images and spatial structure assessed using point pattern analyses with null model comparisons.</p> Results <p>Over five years, <i>P. aliciae</i> expanded its cover from 26 to 73 m² (180% increase) by forming dense clusters of large corals. Mean coral size increased more than threefold (57 cm² to 201 cm²), leading to space limitation within clusters and reduced juvenile abundance. Spatial associations between adults and juveniles reflected episodic recruitment and subsequent competitive exclusion by larger corals, with fusion likely contributing to cluster consolidation. Expansion was driven primarily by the persistence and growth of established corals rather than continuous recruitment.</p> Conclusions <p>Rapid growth, brooding reproduction and spatial clustering likely promote establishment of <i>P. aliciae</i> on temperate reefs of eastern Australia, highlighting the importance of intraspecific interactions in shaping poleward range-edge dynamics of corals.</p>